1. Field of the Invention
The present invention relates to a printed circuit board, and more particularly to a double-sided or multi-layered printed circuit board.
2. Related Art Statement
Conventionally, a method of providing an electromagnetic wave-shielding layer on a printed circuit board via an insulating layer is disclosed in Japanese Patent Laid-Open No. 213192/1987 and is publicly known. As shown in FIG. 3, electromagnetic wave-shielding layers 5 are respectively provided on printed circuits 2 formed on both surfaces of an insulating board 1, via insulating layers 4, and solder resist layers 6 are also provided thereon, thereby forming a printed circuit board 9.
It should be noted that the electromagnetic wave-shielding layers 5 in the printed circuit board 9 are formed in portions excluding plated through-hole portions 7 for conductance by through-holes 8, or part-connecting lands or the like (not shown).
However, in the printed circuit board 9 provided with the conventional electromagnetic wave-shielding layers 5, since part of the electromagnetic wave-shielding layers 5 portions 7, there have been cases where the circuit is affected by electromagnetic waves which can cause passive cr active noise through the conductive through-hole portions 7. In addition, since the continuity of the electromagnetic wave-shielding layer 5 is disrupted by the provision of the conducting through-holes 7, there are cases where it is impossible to obtain a satisfactory effect since the effective area of the electronic wave-shielding layers 5 is reduced.